Incest! I called it!

Not sure I'd call it incest, could very well be that they're husband and wife (If oni even have such a thing)

Whatever though, if a female oni was that hot, you bet I'd hit that lol.

Considering that there is a Japanese proverb that goes "Oni no nyobo kijin go naru" (the wife of an oni grows worse than her mate) I'd say it is a dead certainty they do.

Maybe now we have some idea WHY they grow worse.